1. Field of the Invention
The present invention relates to a charged particle beam instrument.
2. Description of Related Art
Known techniques for performing in situ observations in a gaseous atmosphere by a charged particle beam instrument such as an electron microscope use a diaphragm holder or a differential pumping system.
The former technique using the diaphragm holder makes use of a specimen holder having a space. A diaphragm through which an electron beam can be transmitted is used in this space. This space is filled with a gas. Under this condition, a specimen is observed.
On the other hand, in the latter technique using the differential pumping system, a gas, is directly introduced into a specimen chamber within an electron optical column. An in situ observation is performed while differentially pumping a space partitioned by plates to prevent leakage of gas to surroundings, the plates being provided with orifices to permit passage of an electron beam (see, for example, JP-A-2013-20747).
When an in situ observation is performed using the technique employing a differential pumping system, it is common practice to control a gaseous environment adjuster having gas inlet valves and a pumping system to control the flow of gas.
In the aforementioned technique using a diaphragm holder, it takes a great deal of time to fabricate a diaphragm permitting passage of an electron beam. Also, whenever the specimen is exchanged, a work for replacing or attaching minute parts such as a diaphragm and an O-ring is needed. Furthermore, there is the possibility that the fabricated diaphragm may break suddenly. This creates the danger that the electron microscope will be damaged.
Furthermore, in the technique using a differential pumping system, gas may leak into the specimen chamber via the orifices. Therefore, care has to be exercised in introducing high-pressure gas such that safety is achieved. Additionally, adjustments of the pressure of the introduced gas and venting operations are all performed manually. Therefore, it is impossible to perform these adjustments and operations by unskilled persons. Further, it may take long to make such adjustments.